1. Field of Invention
The present invention relates to a heat dissipation system and a fan thereof and, in particular to a heat dissipation system and a fan thereof including an internal-rotor motor.
2. Related Art
As electronic products progress in their performances, frequencies and calculating speeds and thin sizes, they generate more and more heat in operation resulting in temperature increase. It severely jeopardizes the stability of the electronic products and, meanwhile, reduces their reliability and lifetime. Thus, the heat dissipation has become an important issue for the electronic products. Because fans have advantages of low production cost, technology development and so on, they are frequently used in electronic devices for heat dissipation.
Generally speaking, the fan uses a motor as a power source. The motor includes a rotor magnet, a stator coil and other structures, whose arrangement are used to classify the motors into two major categories, the external-rotor motors and the internal-rotor motors. Recently, the external-rotor motors are applied wildly in industry. However, since their rotor magnets are disposed outside the stator coils and distant from the axle center of the shaft (that is, the rotating radiuses of the rotor magnets in the external-rotor motors are larger), the rotational inertias of the rotor magnets are increased and further larger vibrations are frequently generated at high rotating speed.
Accordingly, as the motor rotates at higher speed, the requirement of the run-out of the rotor magnet is very critical correspondingly. It increases the cost of mold and the difficulty of production. Moreover, if the side run-out of the rotor magnet is too large, the shaft has to bear an even higher impact force resulting from the vibration. In addition, during the external-rotor motor operates at high speed, the heat generated from the copper wire of the stator coil cannot be dissipated effectively and thereby accumulates inside the motor. It shortens the lifetime of the shaft and causes the abnormality of other elements, and further reduces the integral reliability and efficiency of the fan.
In summary, the replacement of the external-rotor motor by the internal-rotor motor to change the position of the rotor magnet can effectively solve most of the aforementioned issues. However, the rotational balance of the internal-rotor motor also has to be adjusted in response to the trend of operation with higher and higher rotating speed. In addition, the heat generated from the copper wire of the stator coil also has to be dissipated effectively to prevent heat accumulation inside the motor resulting in the abnormality of the shaft and other elements. However, no internal-rotor motor able to solve the aforementioned issues appropriately exists nowadays.
Therefore, a heat dissipation system and a fan thereof able to effectively increase the reliability of the motor and prolong the lifetime of the shaft at high rotating speed has been desired.